Trying to join an already exited pthread

[Garrett Cooper]

Garrett Cooper wrote:
> Garrett Cooper wrote:
>> Garrett Cooper wrote:
>>> On Feb 7, 2007, at 1:51 PM, Steve Watt wrote:
>>>
>>>> In <Pine.LNX.4.43.0702071314560.22034 at hymn08.u.washington.edu>,
>>>>  <youshi10 at u.washington.edu> wrote:
>>>>> Just wondering:
>>>>>
>>>>> If I was to try and join a pthread that already exited, would there 
>>>>> be an error
>>>>> message output and/or errno set to an error value, or would a 
>>>>> system hang?
>>>>
>>>> Was the thread created with detach state set PTHREAD_CREATE_DETACHED or
>>>> PTHREAD_CREATE_JOINABLE?  If it was PTHREAD_CREATE_JOINABLE, has the
>>>> thread already been joined?
>>>>
>>>> You should be able to join a thread that was created joinable, only 
>>>> once.
>>>> If you join it again, or join a thread that was created detached, the
>>>> results are unspecified in POSIX.  There is an error status that may
>>>> be returned, but it may do other bad things to your system.
>>>>
>>>> Note that pthread_join doesn't set errno; it returns an error value
>>>> directly.  I would never expect the system to hang, though the 
>>>> application
>>>> might.  If your application is hanging, make sure that you're not 
>>>> trying
>>>> to call pthread_join from within a signal handler.
>>>>
>>>>> It this variable on Unix OSes?
>>>>
>>>> That the results are unspecified?  No.  What "unspecified" means?
>>>> Absolutely.
>>>> --Steve Watt KD6GGD  PP-ASEL-IA          ICBM: 121W 56' 57.5" / 37N 
>>>> 20' 15.3"
>>>>  Internet: steve @ Watt.COM                      Whois: SW32-ARIN
>>>>    Free time?  There's no such thing.  It just comes in varying 
>>>> prices...
>>>
>>>     I asked this because I was short on time and so was the person 
>>> who asked me earlier. I'm going to try giving the pthread exit and 
>>> join a shot just to see whether or not this is true or not and then 
>>> I'll report my results to the list.
>>>     Thanks for the insight though--hopefully my results will yield a 
>>> solid positive or negative to this being a problem.
>>> -Garrett
>>
>> Under Suse Linux there were absolutely no errors when I tried to do 
>> this. I'll post a code snippet later.
>> -Garrett
> 
> Ok, here's a link to my code:
> 
> http://students.washington.edu/youshi10/posted/thread_test.c
> 
> My results (FreeBSD):
> 
> [root at hoover /home/gcooper]# ./tt
> Thread join detached
> Thread kill detached
> Joined thread yielded error code: 2
> Trying to join the already joined thread yields error code: 0
> 
> My results (Suse Linux):
> 
> # ./tt
> Thread join detached
> Thread kill detached
> Joined thread yielded error code: 0
> Trying to join the already joined thread yields error code: 0
> 
> That was sure interesting.. is it supposed to error out or was it the 
> remnant of an old error call?
> 
> Probably the latter, but I was just curious..
> 
> -Garrett